Crank and Cam marks
Thread Starter
Instructor
Joined: Feb 2010
Posts: 118
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From: Ok
Crank and Cam marks
Ok I have spent last hour searching and not finding what I need to know....
So I have taken apart my '72 LT1 due to the valves being floated and bent. I was looking at the cam and crank timing marks and tried to line them up at 6 and 12 and it is not happening. Chain is tight and it dont look like it has slipped.
My question is did they advance or retard the cam from factory????
Car only has 66k miles and chain is tight. Is it possible that when the valves floated it skipped a tooth? Here is a pic.
I have new cloyes dual chain I plan to put on. But was wanting some answers befor I took the stock stuff off.
Thanks in Advance! Jason
So I have taken apart my '72 LT1 due to the valves being floated and bent. I was looking at the cam and crank timing marks and tried to line them up at 6 and 12 and it is not happening. Chain is tight and it dont look like it has slipped.
My question is did they advance or retard the cam from factory????
Car only has 66k miles and chain is tight. Is it possible that when the valves floated it skipped a tooth? Here is a pic.
I have new cloyes dual chain I plan to put on. But was wanting some answers befor I took the stock stuff off.
Thanks in Advance! Jason
Instructor
Joined: Dec 2009
Posts: 109
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From: Nassau co. NY
timing gears/chain
[QUOTE=RacinJason68;1574468708]Ok I have spent last hour searching and not finding what I need to know....
So I have taken apart my '72 LT1 due to the valves being floated and bent. I was looking at the cam and crank timing marks and tried to line them up at 6 and 12 and it is not happening. Chain is tight and it dont look like it has slipped.
My question is did they advance or retard the cam from factory????
Car only has 66k miles and chain is tight. Is it possible that when the valves floated it skipped a tooth? Here is a pic.
I think if it was done on purpose, it would be advanced/retarded way too much using this method. It looks to be a mistake. You have to remove the 3 cam bolts and pop off the cam gear from the camshaft, then slip it out of the timing chain and rotate it one tooth on the chain. Slip it back on the camshaft and reinstall bolts. Torque to spec and use locktite on bolts. That;s it.
Somehow, someone before you must have installed the cam gear one tooth off from being lined up. It is simple once you do it.
Good luck and let us know how it goes.
Greg.
I have new cloyes dual chain I plan to put on. But was wanting some answers befor I took the stock stuff off.
Thanks in Advance!
So I have taken apart my '72 LT1 due to the valves being floated and bent. I was looking at the cam and crank timing marks and tried to line them up at 6 and 12 and it is not happening. Chain is tight and it dont look like it has slipped.
My question is did they advance or retard the cam from factory????
Car only has 66k miles and chain is tight. Is it possible that when the valves floated it skipped a tooth? Here is a pic.
I think if it was done on purpose, it would be advanced/retarded way too much using this method. It looks to be a mistake. You have to remove the 3 cam bolts and pop off the cam gear from the camshaft, then slip it out of the timing chain and rotate it one tooth on the chain. Slip it back on the camshaft and reinstall bolts. Torque to spec and use locktite on bolts. That;s it.
Somehow, someone before you must have installed the cam gear one tooth off from being lined up. It is simple once you do it.
Good luck and let us know how it goes.
Greg.
I have new cloyes dual chain I plan to put on. But was wanting some answers befor I took the stock stuff off.
Thanks in Advance!
Thread Starter
Instructor
Joined: Feb 2010
Posts: 118
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From: Ok
Well the motor has never been out.. I pulled it. Original motor. Sooo. I am thinking it slipped unless it is a factory adjustment. But dont see that being the cause.
I know how to fix it, just curious anyone ran across this issue.
I know how to fix it, just curious anyone ran across this issue.
Instructor
Joined: Dec 2009
Posts: 109
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From: Nassau co. NY
Oh. I see. Well, is there enough slack in the chain to slip a tooth , do you think? I don't see why they would set it like that. like I said, I think that is alot more advance/retard moving one tooth. When you get the aftermarket adjustable timing sprocket, they adavance/retard the cam by using the keyways in different ways, yielding less movement than one tooth.
I don't know what to tell you, but good luck.
I don't know what to tell you, but good luck.
Thread Starter
Instructor
Joined: Feb 2010
Posts: 118
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From: Ok
yeah think some how it slipped when the valves hit... Only thing I can think of. It bent basicly every valve, and happened at a very high rpm....
Strange thing is usually it seems like you can see the gears that have been slipped. It is pretty darn tight..
confused. Thinking just install the new chain and gears and move on... LOL
Strange thing is usually it seems like you can see the gears that have been slipped. It is pretty darn tight..
confused. Thinking just install the new chain and gears and move on... LOL
Instructor
Joined: Dec 2009
Posts: 109
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From: Nassau co. NY
yeah think some how it slipped when the valves hit... Only thing I can think of. It bent basicly every valve, and happened at a very high rpm....
Strange thing is usually it seems like you can see the gears that have been slipped. It is pretty darn tight..
confused. Thinking just install the new chain and gears and move on... LOL
Strange thing is usually it seems like you can see the gears that have been slipped. It is pretty darn tight..
confused. Thinking just install the new chain and gears and move on... LOL
That's probably what I would do also at this point. Maybe a good time for a nice roller set.
Race Director
Joined: Jan 2000
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From: Corsicana, Tx
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Somebody has been in there before it looks like. It had to run pretty funky that way.
Install all your new parts and have at it. Is it time for a cam upgrade too?
JIM
Install all your new parts and have at it. Is it time for a cam upgrade too?
JIM
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Thread Starter
Instructor
Joined: Feb 2010
Posts: 118
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From: Ok
Well not sure, it belonged to my dad befor hand and he never cracked it open.... So...
Cam upgrade? Thought the factory LT1 cam was pretty good. Am I wrong? Everyone keeps sayin to keep it stock. LOL I plan to go back stock with about everything.
Cam upgrade? Thought the factory LT1 cam was pretty good. Am I wrong? Everyone keeps sayin to keep it stock. LOL I plan to go back stock with about everything.
Melting Slicks
Joined: Oct 2002
Posts: 2,317
Likes: 111
From: St Louis MO
Sorry to hear of your misfortune...
Your cam timing is retarded by one tooth. There are 18 teeth on the crank gear, so the cam is shifted by 20 degrees. If the cam and cam timing set was set up to install the cam at 4 degrees advanced, you have been running instead with 16 degrees of camshaft retard.
I'd expect only the exhaust valves to be bent since the rising piston chases the late exhaust valve closing, but the intakes are probably not bent because late opening intake valves chase a rapidly descending piston.
Can you post any pictures of the heads & bent valves?
Your cam timing is retarded by one tooth. There are 18 teeth on the crank gear, so the cam is shifted by 20 degrees. If the cam and cam timing set was set up to install the cam at 4 degrees advanced, you have been running instead with 16 degrees of camshaft retard.
I'd expect only the exhaust valves to be bent since the rising piston chases the late exhaust valve closing, but the intakes are probably not bent because late opening intake valves chase a rapidly descending piston.
Can you post any pictures of the heads & bent valves?
Race Director
Joined: Nov 2002
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From: Taylor Michigan
LT1 cam is a good choice, but run it straight up...leave the fancy stuff to the Pros
Melting Slicks
Joined: Apr 1999
Posts: 2,010
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From: Moon Twp. PA USA
12 o'clock on the crank gear, and 6 o'clock on the cam gear is NOT TDC firing position on #1 cylinder. 12 o'clock on each gear is.
If you set at 12 & 6 o'clock you must rotate the engine 1 turn to have #1 cylinder at TDC firing position. Dots will both be at 12 o'clock.
If you set at 12 & 6 o'clock you must rotate the engine 1 turn to have #1 cylinder at TDC firing position. Dots will both be at 12 o'clock.
Melting Slicks
Joined: Mar 2007
Posts: 2,520
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From: Hinckley OH
It's hard to tell from the picture, but, it looks like the mark on the crank is not exactly at 12:00. Also, it looks like the key on the crank might be a little deformed. Where do they need to be to line up the marks? Some pics with the cam at 12:00 would be helpful.
Safety Car
Joined: Mar 2007
Posts: 3,652
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From: Bridgewater nj
If that engine was running well at low RPMs with that timing chain I would definately put a cam wheel on your crank w/ a piston stop. With the cam that far retarted it would have no torque but it would scream pretty good
I have seen chains jump a tooth and that timing set is in way too good of shape to jump a tooth. Someone did that on purpose or just F-up.
I have seen chains jump a tooth and that timing set is in way too good of shape to jump a tooth. Someone did that on purpose or just F-up.
Thread Starter
Instructor
Joined: Feb 2010
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From: Ok
Well the intake and exhaust valves were bent. I am not 100% sure and cant ask now, but dad never said anything about being in that motor, till he floated the valves and took the heads off. There it set for 23 years till I got it. So possible someone in there befor, maybe but not sure how it would have ever ran worth a damn afterwards and I know he had been driving it for quite awhile befor the late night "valve floating" ordeal.
I guess at this point I will just clean it all up and install new chain and set it at 0*.
I guess at this point I will just clean it all up and install new chain and set it at 0*.
Safety Car
Joined: Mar 2007
Posts: 3,652
Likes: 49
From: Bridgewater nj
Sounds like a plan Jason but like I stated before. Get a degree wheel and verify top dead center so you are sure everything from the timing marks to the distributor is on the money. Degree wheels are cheap and a little research on how to use it will make it easy to use
Pro
Joined: Jul 2005
Posts: 517
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From: Peoria IL
Look Jim, that never 'cracked' 350 in the picture has a steel gear....GM uses a nylon upper gear as OE equipment so someone has been in it. I would think that the valves bent were all the exhaust if there was bent valves in the first place as the piston always chases the exhaust valve home and retarding the cam brings them much closer......
LT1 cam is a good choice, but run it straight up...leave the fancy stuff to the Pros
LT1 cam is a good choice, but run it straight up...leave the fancy stuff to the Pros
Le Mans Master
Joined: Oct 2002
Posts: 7,098
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From: Las Vegas - Just stop perpetuating myths please.
Thats not the right way to advance the cam.
U need to align the marks and i u want to degree the cam in u will need to install a degree wheel to measure with. Adjusting is by drilling out the cam gear locating pin hole and using busing to advance or retard the cam.
Good luck,
cardo0
Sorry to hear of your misfortune...
Your cam timing is retarded by one tooth. There are 18 teeth on the gear, so the cam is shifted by 20 degrees. If the cam and cam timing set was set up to install the cam at 4 degrees advanced, you have been running instead with 16 degrees of camshaft retard.
I'd expect only the exhaust valves to be bent since the rising piston chases the late exhaust valve closing, but the intakes are probably not bent because late opening intake valves chase a rapidly descending piston.
Can you post any pictures of the heads & bent valves?
Your cam timing is retarded by one tooth. There are 18 teeth on the gear, so the cam is shifted by 20 degrees. If the cam and cam timing set was set up to install the cam at 4 degrees advanced, you have been running instead with 16 degrees of camshaft retard.
I'd expect only the exhaust valves to be bent since the rising piston chases the late exhaust valve closing, but the intakes are probably not bent because late opening intake valves chase a rapidly descending piston.
Can you post any pictures of the heads & bent valves?
Race Director
Joined: Jan 2000
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From: Corsicana, Tx
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Ironcross...that's what I meant. No steel gears factory on those motors that I know of. Some later truck motors..but not the car ones. It was very common to change them before too many miles.
If it's an LT-1 cam...then that's a good piece for the street. Keep what you have.
JIM
If it's an LT-1 cam...then that's a good piece for the street. Keep what you have.
JIM